1. Field of the Invention
This invention refers to marine platforms destined for use as supports for any type of industrial installations, such as warehouses, chemical or physical treatment plants, energy production sites, etc.
The invention is particularly adapted for marine platforms mounted in shallow water areas. Henceforth, shallow water areas shall mean areas where the water is no more than 40 meters in depth.
The invention is also applicable to floating land foundations in seismic areas, as will be explained hereinafter.
2. Description of the Prior Art
The feasibility of mounting certain installations on marine platforms is stirring greater interest day by day. This is due, in some cases, to the pollutant and hazardous aspects of certain plants, such as chemical installations in general, nuclear centers, etc., in other cases, to the facilitated loading and unloading of the treatment product when it is transported via ship, and, in still other cases, to areas where not enough land is available to mount the installation.
Even greater interest is aroused by platforms that are capable of floating and being transported with the mounted installation, inasmuch as this allows the construction and mounting of an industrial installation in an industrialized nation in such a way that the cost and time of delivery are kept to a minimum and may be forecast rather accurately. Then, the platform is floated to the delivery site, which, in many cases, is not equipped with the best means to construct and mount the installations.
Another advantage of industrial installations mounted on floating platforms is that they may be used in locations where their operation or installation will only be temporary. This may be the case in the utilization of prime materials coming from small deposits. The platform, together with its installation, may then be moved to another location.
Floating platforms are primarily conceived to operate in one of the following manners: floating or resting on the ocean floor.
Floating platforms present a disadvantage because of continual movements and possible displacements due to waves, currents, tides, and winds.
These displacements greatly complicate the connections for the transport of the treatment product to and from the platform, making it necessary to rely on extremely complex solutions, especially when the product in question is hazardous at high pressure or low temperature.
The problem becomes even more acute when the treatment product is transported to or from a ship, inasmuch as in addition to the possible movements of the platform, those of the boat must also be contended with.
Movements of the platform also require a modification of the procedures normally used on land, rendering the installation more costly. It may also be necessary to suspend its operation in the case of adverse maritime conditions.
Platforms that operate while resting on the ocean floor avoid the problems mentioned in relation to the floating platforms.
Spanish Pat. No. 451,827 describes a marine platform, capable of floating, and designed to operate while resting on the ocean floor in shallow water areas. It is constructed so that it may be floated up whenever necessary either for relocation by floating to another site or for inspection and maintenance purposes.
In accordance with said patent, the platform consists of a lower keel, made, e.g., of a concrete case, which rests on the ocean floor and a barge which, in turn, rests on the keel.
Both the barge and the keel have ballast tanks which allow foundering and floating, wherever desired, for transport to another location by flotation.
To avoid the appearance of certain stresses between the contact surfaces of the barge and the keel, a stratum of deformable material is placed on the keel, e.g., gravel or the like, assuring uniform contact between said barge and keel.
The keel shall be of a height that the barge with empty ballast tanks may float upon said keel. When the ballast tanks are full, the barge rests on the keel with enough pressure so as to hinder movements of the barge by external forces.
In other words, the barge and the keel remain connected due to the weight of the barge and the composition or nature of the deformable stratum placed between the barge and keel.
This system of mounting the barge presupposes that, in the case of an earthquake, both the horizontal and the vertical movements, as well as the amplified horizontal movements or oscillations, of the keel are transmitted entirely to the barge. These oscillations, particularly the horizontal, may endanger the stability of the installation mounted on the barge, even to the point of destruction should the earthquake be of a certain magnitude.
If the friction between the barge and keel were not enough to ensure that the barge would follow the keel in its oscillations due to earthquakes, the barge would undergo uncontrolled displacements and irreparable damage with respect to the keel, which displacements could even lead to the fall of the barge.